This invention relates to limited rotation motors of the moving coil or d'Arsonval type. One function of such motors is to move a stylus or pen in conjunction with a recording instrument or the like and thus may be utilized to document the intensity of various input signals.
In the construction of such motors it is necessary that the magnet be precisely positioned with respect to the stator such that a magnetic field space of known dimensions is formed therebetween. Additionally, it is also necessary that the moving coil be positioned so as to freely arcuately move back and forth within such space without contacting either the stator or the magnet. To accomplish such, it has been generally necessary during the assembly of such motors to first independently attach a plate to both end faces of the magnet as by a permanent adhesive connection and then position a pair of brackets in which the coil is rotatably journalled both with respect to the stator and the magnet. This manner of assembly requires considerable trial and error positioning, is time consuming and can lead to inaccuracies.
It would accordingly be desirable to be able to reduce the effort and number of steps required in accurately mounting the magnet and moving coil components of such motors. It is accordingly a principal object of the present invention to provide a positioning device which reduces the time and effort in such aforementioned assembly by simultaneously positioning the magnet and the coil with respect to each other and said stator.
This and other objects of the invention are accomplished by the provision of a pair of bridges laterally spanning the opposite end faces of the stator and in which the coil is previously journalled in a predetermined position with respect thereto. The bridges include a first pair of inwardly extending pins adapted to contact the side surfaces of the magnet in side-to-side longitudinal contact so as to position them laterally with respect to the stator in a first, i.e. horizontal, direction. The bridges further include a pair of second pins also inwardly extending and in contact with an undercut slot provided in the opposite end surfaces of the magnet so as to position the magnet in a second, i.e. vertical, direction with respect to the stator. Inasmuch as the pins form an integral portion of the bridges, mounting of the bridges simultaneously assures the proper positioning of both the magnet and coil with respect to each other and the stator opening.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawing.